1. INSECTS

2. What happens to a body immediately after death?

3. What happens to a body immediately after death?
1. Algor mortis - change in temperature after death
2. Livor mortis - setting of blood gives bluish-purple colour
3. Rigor mortis - stiffening of muscles
4. Autolysis - tissue breakdown by enzymes
5. Putrefaction - tissue breakdown by bacteria - characteristic odour
6. Mummification - dehydration/desiccation of tissues

4. Succession on a corpse
Post mortem Processes
1. Initial Decay - body appears ‘normal’ but is decaying internally
2. Putrefaction - cadaver is swollen from internally produced gases
3. Black Putrefaction - exposed skin - black, body collapses
4. Dry Decay - cadaver nearly dry - slow rate of decay

5. There are two main ways of using insects to determine elapsed time since death :
1. using successional waves of insects
2. using maggot age and development.

7. Succession on a corpse
1: Within minutes - hours Calliphora and Lucilia spp - primary species
-lay eggs in natural body openings (ears, nostrils, eyes or wounds)
1: Within hours-days Chrysosoma and Sarcophaga spp - secondary species
face competition from primary species
compensation: viviparity

8. Estimating PMI
1. Temperature dependent development of insects
- insect developmental rate  ambient temperature
- development will not occur below a species-specific threshold temperature
- the accumulation of heat can be expressed as “degree-days” or “degree-hours”
Problem: little work done on the daily temperature fluctuations and development

9. Estimating PMI
Development times and temperature
Calliphora vomitoria
Stage 12.5ºC 23ºC 29ºC 35ºC
Egg
Instar

10. Estimating PMI 20
Maggot length 10 mm
Crop length
Time from last feeding (h)

11. Estimating PMI
Experimental Evidence
Take larvae from body
Raise to adult in lab
Mate insects and allow to lay eggs
Incubate at field temperatures
Note time taken to get to
stages collected in field

12. Two kinds of developmental data
1. Lab Experiments
-as in previous slide
2. Field Observations
Wind speed & direction
Minimum & Maximum temperatures
Developmental Degree-days
Relative humidity
Cloud cover
Precipitation

13. Who are these insects?
1. Calliphoridae (blow flies)
2. Muscidae (muscid flies)
3. Silphidae (carrion beetles)

14. Who are these insects?
4. Sarcophagidae (flesh flies)
5. Histeridae (clown beetles)
6. Staphylinidae (rove beetles)

15. Who are these insects?
7. Nitidulidae (sap beetles)
8. Cleridae (checkered beetles)
9. Dermestidae (dermestid beetles)

16. Who are these insects?
10. Scarabaeidae

17. Succession of adult insects on cadavers in Tennessee (spring/summer)
Succession of larval insects on cadavers in Tennessee (spring/summer)
Family Fresh Bloated Decay Dry
Calliphoridae
Muscidae
Silphidae
Sarcophagidae
Histeridae
Staphylinidae
Nitidulidae
Cleridae
Dermestidae
Scarabaeidae

18. Invertebrates Associated
with Cadavers

19. Some case studies:
Case 1:
Victim: 14-year old prostitute
Found: Wooded lane in NW U.S. – 4 June
Reported missing 4 days earlier
Problem – no precise time of death
Data/specimens gathered:
Climatic data
Adult flies and eggs/larvae from wounds
All other insects
Entomologists – calculated that first insects got to body on 31 May.

20. Some case studies:
Case 2:
Victim: 30 year old female
Found: In parking lot at 6 AM (New England)
No insects present
As day warmed – greenbottle fly (Phaenicia)
appeared and fed around woulds
Soon after – clusters of eggs
Key facts
-flies aren’t night active
-previous day – ideal for fly activity
Conclusion: Victim killed during preceding hours of darkness

21. Some case studies:
Case 3:
Victim: 46 year old male alcoholic
Found: In bedroom
Dead: 5 days
Found eggs larvae + red pupae on corpse – incubated them and got Muscina stabulans
Determined from rearing experiments that the development time for this species 28 days (egg to adult at 16 C)
Tested to see what redness was in pupae – Serratia marcescens
Conclusion: Victim was ill with Serratia infection before he died and flies laid eggs while he was still alive

22. Aquatic insects to establish PMI

25. Other uses for insects in forensics
1. Detection of poison, drugs and other chemicals
Phenobarbitol
Mercury
Cocaine
Heroin
Malathion
2. Determination if an insect is the “criminal”
3. Determination of sequence of events in a crime